1. Field of the Invention
The present invention relates to a video signal processing apparatus for processing a video signal to obtain a print image from the video signal.
2. Description of the Prior Art
FIG. 1 shows a block diagram of an example of an arrangement of a conventional video printer for processing a video image. An input video signal 1 is converted to a digital signal by an A/D converter 2 and is processed to become a printing signal by an image processing circuit 3 and is printed by a printer 4.
Next, the case where a print size is switched using this apparatus will be assured. FIG. 2 shows a situation wherein the number of sample points of the image data is doubled as compared with the original image and the print size is doubled (i.e., the area covered is increased four times) and an arrangement block diagram of a video printer suitable for use in this case is shown in FIG. 3. In FIG. 3, the similar (corresponding) components as those shown in FIG. 1 are designated by the same reference numerals. The input video signal 1 is converted to a digital signal by the A/D converter 2 and an interpolation of the data is performed by an interpolating circuit 10. The interpolated data is processed by the image processing circuit 3 to become the printing signal and is printed by the printer 4. The interpolating circuit 10 converts image data 5 and 6 in FIG. 2 to image data 7, 8 and 9, respectively. It is assumed that the image data 7 is the same as the image data 5 and the image data 9 is the identical to the image data 6, while the intermediate image data 8 is the data which is inserted between the image data 5 and 6. In the case of a linear interpolation, the image data 5 and 6 are added and the quotient of the sum was divided by two is used as the image data 8. The interpolation is performed in the foregoing arrangement and the print size of the image is changed over.
However, such an interpolation requires memories, adders and dividers since additions and divisions of at least two pixels are executed in both horizontal and vertical directions of the picture plane, so that there are the drawbacks that the hardware becomes complicated and expensive and that the timings for data processes also become complicated.